spec•trum (spek'trem)

noun pl. spectra spec·tra (-trə) or spec·trums

Physics The distribution of a characteristic of a physical system or phenomenon, especially:a. The distribution of energy emitted by a radiant source, as by an incandescent body, arranged in order of wavelengths.
b. The distribution of atomic or subatomic particles in a system, as in a magnetically resolved molecular beam, arranged in order of masses.
A graphic or photographic representation of such a distribution.
a. A range of values of a quantity or set of related quantities.
b. A broad sequence or range of related qualities, ideas, or activities: the whole spectrum of 20th-century thought.
Origin: Latin, appearance, from specere, to look at; see spek- in Indo-European roots.